public static function createProcess($inputformat, $outputformat, $apikey = null)
 {
     $instance = new self();
     $instance->apikey = $apikey;
     $data = $instance->req('https://api.cloudconvert.com/process', array('inputformat' => $inputformat, 'outputformat' => $outputformat, 'apikey' => $apikey));
     if (strpos($data->url, 'http') === false) {
         $data->url = "https:" . $data->url;
     }
     $instance->url = $data->url;
     return $instance;
 }